INHIBITION BY ALUMINUM ION OF NAD-DEPENDENT AND NADP-DEPENDENT ISOCITRATE DEHYDROGENASES FROM YEAST

1. NADP-dependent isocitrate dehydrogenase from yeast was potently inhibited by aluminum ion competitively with respect to the substrate isocitrate, and noncompetitively with the other substrate NADP. K(i) value was determined to be 0.43-mu-M. 2. Aluminum ion acted as only a weak allosteric inhibitor of yeast NAD-dependent isocitrate dehydrogenase toward isocitrate, and as a noncompetitive inhibitor toward NAD. 3. Inhibition by aluminum ion of NADP- and NAD-isocitrate dehydrogenases can reduce the aerobic energy production in yeast, and may contribute to the biological toxicity of aluminum in ecosystems and human life.